Question

Morgan bred a white-eyed male with a red-eyed sister, and obtained all red-eyed offspring. These red-eye off-spring were then intercrossed. From which Morgan observed a 2459 red-eyed females, 1011 red-eyed males and 782 white-eye males. This is a 2:0:1:1 ratio compared to an expected ratio of 3:1:3:1 (red eye female, white eye female, red eye male, white eye male).

1. Use a Chi-squared test to analyze whether the differences between the observations and the expectations are due to random variation? What is the chi-squared number?

2. Are these observations due to chance?

A. No, p-value <0.5

B. Yes, p-value <0.5

C. No, p-value >0.5

D. Yes, p-value >0.5

E. Can not be determined, you need more information.

3. What are the genotypes of the F2 progeny?

Answer 1

1)

category	observed frequencey, O		expected frequency,E			(O-E)²/E
red eye female	2		3.00			0.333
white eye female	0		1.00			1.000
red eye male	1		3.00			1.333
white eye male	1		1.00			0.000

chi square test statistic,X² = Σ(O-E)²/E =   2.667              
                  

2)

level of significance, α=   0.05              
Degree of freedom=k-1=   4   -   1   =   3
                  
P value =   0.4459   [ excel function: =chisq.dist.rt(test-stat,df) ]          

Decision: P value >α , Do not reject Ho     

D. Yes, p-value >0.5